Add a basic test for the validation client due to codecov

test/Client/Exception/Validation.php

@@ -0,0 +1,35 @@
+<?php
+declare(strict_types=1);
+
+namespace VonageTest\Client\Exception;
+
+use PHPUnit\Framework\TestCase;
+use Vonage\Client\Exception\Exception;
+
+class Validation extends TestCase
+{
+    public function testValidationException()
+    {
+        $message = 'Validation failed';
+        $code = 422;
+        $previous = new Exception('Previous exception');
+        $errors = [
+            'field1' => 'Error message 1',
+            'field2' => 'Error message 2'
+        ];
+
+        $exception = new Validation($message, $code, $previous, $errors);
+
+        // Assert the exception message
+        $this->assertEquals($message, $exception->getMessage());
+
+        // Assert the exception code
+        $this->assertEquals($code, $exception->getCode());
+
+        // Assert the previous exception
+        $this->assertSame($previous, $exception->getPrevious());
+
+        // Assert the validation errors
+        $this->assertEquals($errors, $exception->getValidationErrors());
+    }
+}